1. Field of the Invention
This invention pertains, in general, to the field of retractable covers or roofs for large structures, such as athletic stadiums. More specifically, the invention relates to an improved transport mechanism for such a structure that is more compact, reliable, stable, mechanically simple and inexpensive to construct than comparable mechanisms heretofore known.
2. Description of the Related Technology
It is common these days for athletic stadiums to be constructed with retractable roofs, because this type of construction offers spectators the pleasure of being outdoors on pleasant days, while providing shelter when necessary against extreme temperatures and inclement weather conditions. In addition, retractable roof construction permits the use of natural grass in a stadium, which is very important to most athletes.
A number of factors must be taken into account in the design of a stadium that has a retractable roof. For instance, the forces created by the exertion of natural forces such as wind, rain snow and even earthquakes on such a large structure can be enormous, and the roof, the underlying stadium structure and the transport mechanism that is used to guide and move the roof between its retracted and operational positions must be engineered to withstand the worst possible confluence of such forces. In addition, for reasons that are both aesthetic and practical, it is desirable to make the structural elements of the roof and the transport mechanism to be as unobtrusive and as space-efficient as possible. It is desirable to make the roof structure and the transport mechanism to be as simple and maintenance-free as possible, and to be constructed so as to be able to open and close as quickly as possible.
Many cities in the United States and elsewhere are now using or building retractable roofed stadiums. The designs of the various stadiums are quite different, but there are a number of deficiencies that seem to be common to all of the designs that have been implemented thus far. For example, the transport mechanisms in most of the stadiums tend to be quite large, being as much as twenty to thirty feet in height. The transport mechanisms further tend to include a relatively small number of very large, heavily loaded wheels and bearings, and a small number of very large motors or actuators to drive the roof between the retracted and operational positions. The small number of large wheels exert very large concentrated loads onto the support structure, which requires the support structure to be heavily reinforced, adding to the cost and complexity of the stadium as a whole. The roof and transport mechanisms in existing designs further tend to be relatively heavy and inflexible, and often experience alignment problems during movement. While many of these problems have been eliminated through the efforts of Uni-Systems, Inc., as is disclosed in U.S. patent application Ser. No. 09/140,718, the entire disclosure of which is hereby incorporated as if set forth fully herein, additional improvements are possible and are sought after by Uni-Systems, Inc. and others.
Environmental forces that are constantly at work on these massive structures exacerbate the alignment problems. For example, temperature differentials will cause different areas of the roof members, transport mechanisms and the underlying structures to expand and contract unpredictably. Settling of the foundation and other portions of the stadium will occur over time, adding to the alignment problems. Most importantly, winds acting on the roof structure can cause a large section of roof to move, often by several inches. While reinforcement can reduce the amount of such movement, it will add to the weight and expense of the structure.
A need exists for an improved design for a stadium that has a retractable roof and transport mechanism that is compact, lightweight and mechanically simple, and that is capable of maintaining its stability and alignment during normal use and in extreme conditions more capably than comparable mechanisms heretofore known.
Accordingly, it is an object of the invention to provide an improved design for a stadium that has a retractable roof and transport mechanism that is compact, lightweight and mechanically simple, and that is capable of maintaining its stability and alignment during normal use and in extreme conditions more capably than comparable mechanisms heretofore known.
In order to achieve the above and other objects of the invention, a system according to a first aspect of the invention for supporting a large structural member for stable movement with respect to an underlying structure includes a transport mechanism that is constructed and arranged to permit the large structural member to move in a predetermined path with respect to the underlying structure; and orientation structure for maintaining the transport mechanism in a predetermined orientation while simultaneously permitting a limited amount of movement of the large structural member in a direction that is nonparallel to the predetermined path
According to a second aspect of the invention, an edifice having a movable roof member includes an underlying structure; a roof member; a transport mechanism that is constructed and arranged to permit the roof member to move in a predetermined path with respect to the underlying structure; and orientation structure for maintaining the transport mechanism in a predetermined orientation while simultaneously permitting a limited amount of movement of the roof member in a direction that is nonparallel to said predetermined path.
A stadium according to a third aspect of the invention and having a movable roof member includes a main stadium edifice having a first roof support area, a second roof support area, and an open area therebetween; a first transport mechanism mounted on said first roof support area, said first transport mechanism being constructed and arranged to permit movement along a first path; a second transport mechanism mounted on said second roof support area, said second transport mechanism being constructed and arranged to permit movement along a second path that is substantially parallel to said first path; a roof member supported at first and second locations, respectively by said first and second transport mechanisms; and orientation structure for permitting a limited amount of movement of at least a portion of said roof member in a direction that is nonparallel to said first and second paths without affecting either of said transport mechanisms.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.